Smart objects are devices whose primary function is augmented with intelligent behavior and communication capabilities. Many everyday devices can be utilized more effectively, or in new ways, by embedding some intelligence in them. This trend is already apparent in some lighting products for the home and office market. Examples are daylight sensing or presence detection. These are simple examples of combining several objects with communication capabilities and making them more than the sum of their parts. As more and more devices will be equipped with micro processors and communication capabilities, more complex inter-device behaviors will emerge.
In order to control a luminaire or other load devices, it is very common today to send control signals from a (central) controller to the luminaire. For example, Digital Addressable Lighting Interface (DALI) and Digital Multiple (DMX) are very well known protocols to send commands for e.g. dimming from a light controller to a luminaire. DALI or DMX signals are distributed to the luminaires by wires and the luminaires are connected to the mains by separate and different wires.
A very likely candidate for a new communication backbone is the Internet, enabled through Ethernet or other LAN networking. Ethernet has the major advantage that it is everywhere, and due to the massive volumes involved, equipping a device with Ethernet communication means can be easily done at low costs. Ethernet was developed around 1975 by Xerox and has seen multiple upgrades and improvements since. Ever since Ethernet transitioned to the well known 8P8C/10BASE-T (or RJ45) connector and cabling, it has enjoyed full backward compatibility with older devices. Due to the enormous amount of devices compatible with this technology, this form of Ethernet is supposed to survive for many more years.
Most traffic on Ethernet networks is comprised of Internet Protocol (IP) packets. The Internet Protocol, standardized into RFC 791 around 1981, is the backbone of the Internet today. It allows packets to travel on this network in an efficient and robust way. More and more devices are joining the Internet, and most of them are not traditional personal computers (PC's) or laptops. The cellphone revolution put a communication device in everyone's pocket. The current smartphone revolution will connect everyone permanently to the Internet. This means that everyone carries devices that can interact with smart objects around us in several ways.
A very interesting recent addition to Ethernet is the capability to also deliver DC power over the Ethernet cables, while remaining fully compatible with equipment that does not make use of this. First standardized in 2003, the IEEE 802.3af standard allows up to 15 W of consumption by the Ethernet device. A second standard developed in 2009 pushes this to 25 W of power. The reason for this conservative limit is the desire to be compatible with thick bundles of cable. For some use cases this is not a requirement and manufacturers have created higher power Power over Ethernet (PoE) extensions. Power supply manufacturers are even offering products that deliver up to 95 W per Ethernet port or a power module with power transfer capabilities of up to 200 W over a single Ethernet cable. These high power extensions to PoE (not compliant with any IEEE standard, but usually providing a level of compatibility) are mostly used for emerging applications such as PoE laptops, televisions and high performance cameras. Although such power levels clearly require consideration on cable layout, it provides the potential to power even very powerful luminaries directly from the Ethernet switch.
PoE is a standardized way to transfer power and data to a device. PoE is increasingly used for e.g. surveillance cameras, Voice over IP (VoIP) phones, computer monitors and even luminaires. It can be used for all kinds of low power loads like lighting equipment (sensors, switches, light sources etc.) or entertainment appliances like active speakers, internet radios, DVD player, set-top boxes and even TV sets. An advantage of this is that the power and the control data are transmitted through the same cable. This means that it is not necessary to install separate cables for power and for data (as is the case if data is provided by e.g. DALI). For PoE, Cat5 cables can be used. These cables are generally available in a wide variety of lengths and at very low cost. Alternatively Cat6 or Cat7 cables can be used.
Most PoE switches offer the possibility to manage the ports through commands according to the Simple Network Management Protocol (SNMP). SNMP enables e.g. the following functions:
switching on and off specific ports;
measuring the power that a PoE device is drawing from a specific port; and
setting timers to switch on/off ports at a given time:
FIG. 1 shows a schematic architecture of a PoE lighting installation. Two sets of N luminaires 10-1 to 20-N and 22-1 to 22-N are connected to respective PoE switches 10, 12 and data (Ethernet) and power (PoE) are transmitted from the PoE switches 10, 12 to each luminaire by a Cat5 cable (or any other multiple wire cable). N can be any value, typically N may be in the range of 4 to 48. In the example of FIG. 1, power is supplied to the PoE switches 10, 12 via a power supply grid 110 and wired Ethernet is provided at each PoE switch via an Ethernet connection or bus 120. However, an Internet connection could also be provided via wireless connections. In FIG. 1, the two PoE switches 10, 12 are daisy chained by Cat5 cables to provide Ethernet to each PoE switch 10, 12. Either PoE switch has its respective luminaires 20-1 to 20-N or 22-1 to 22-N connected to it, but this could also be a combination of luminaires and other PoE devices. In the example in FIG. 1 there are two sensors 30, 32 connected to detect e.g. occupancy or the presence of daylight. The sensors 30, 32 can give commands to a specific subset of luminaires, e.g. to switch on when presence is detected.
FIG. 2 shows a more detailed architecture of the PoE lighting system of FIG. 1 with the PoE switch 10, luminaires 20-1 to 20-N and a user interface (UI) 40. A similar architecture is disclosed in the WO 2012/028981 A1, for example. In one luminaire 20-1 a driver 202 is shown. The drivers of the other luminaires are not shown. In the PoE switch 10 a power supply unit (PSU) 102 is indicated. Each luminaire 20-1 to 20-N and 22-1 to 22-N contains the driver 202 to apply the right current and voltage to the light source(s) which may be light emitting diodes (LEDs), phosphor converted LEDs, organic LEDs (OLEDs), laser diodes, phosphor converted laser diodes, fluorescent lamps, halogen lamps, high intensity discharge (HID) lamps and/or Ultra High Performance (UHP) lamps. The driver 202 may in general be dimmable and may dim according to signals that it receives from the UI 40. Also switching the light on and off can be controlled by data that are provided via the Ethernet connection. The UI 40 can be a PC that is connected to the PoE switches 10, 12 via Ethernet and that runs appropriate software to generate commands for the luminaires 20-1 to 20-N (e.g. dimming, switching on and off, etc).
Alternatively the UI 40 can be a dedicated device (e.g. a panel) providing the control data for the luminaires 20-1 to 20-N via the Ethernet connection 120.
The IP-controlled luminaires 20-1 to 20-N offer many advantages, as described above. However, the cost is high due to the need for Ethernet in each luminaire. In addition, when the luminaires 20-1 to 20-N are switched off, there is still some power consumption in the system since Ethernet is still active in each luminaire and since the PSU 102 in the PoE switch 10 is still on.
A further disadvantage is the size of the driver 202 that has to be accommodated in the luminaires 20-1 to 20-N. For some luminaire types this size is no issue, but for some luminaire types, miniaturization is a value driver.
US 2010/0171602 A1 discloses a management agent which has access to power output control circuitry of a digital electronic communication switch, a power meter, a load sharing means, and the ability to manage the power of switching circuits in the switch. The power meter enables the management agent to identify the power consumed by the switching circuits that are enabled and operational. This information, coupled with knowledge of the power allocated to each port via PoE, and policy information which specifies power allocation preferences is used in a two-pass power management method.